1. Field of the Invention
The present invention relates generally to the meniscus coat printing of stripe or line screens for luminescent video displays, such as may be found, for example, on color cathode ray tubes (CRTs).
2. Discussion of the Related Art
In the art of CRT screen application there are known many forms of screen deposition. Among these are the well known photolithographic techniques for color screens wherein photosensitive slurries containing the luminescent phosphors are spin coated to the faceplates and exposed to light wavelengths actinic to the photosensitive slurry, whereupon the exposed pattern of slurry is washed and baked. In color CRT screens serial light exposures are made to form each of the grille, or black matrix, pattern and red, green and blue phosphor patterns hereinafter generically referred to as "screen elements". Spin coating can result in slurry waste, skirt or mask support contamination, and uneven coating thickness. Photolithographic exposure takes numerous time consuming steps.
So called "silk screen" printing is also utilized wherein a phosphor containing paste, is squeegeed through a wire form to print the screen. Multiple passes for each phosphor and grille element of the color CRT screen must also be made. The wire form can be subject to distortion when the squeegee presses the paste there through thereby causing a distortion of the screen pattern.
Printing of the direct contact, or offset, type has also been proposed. Registration and repeatability of the screen elements is considered somewhat problematical for the alignment of each phosphor and grille element in single or multiple pass applications due to the distortion of the print blanket media owing to the pressure of contact on the glass faceplate. Further, the substrate must be very uniform to accept a complete transfer of phosphor inks from the print blanket.
Therefore, it will be seen that of the prior art methods discussed, all have drawbacks in relation to either the amount of processing steps, the waste of materials, or registration and alignment from the multiplicity of screen element applications needed with a deformable apparatus. All known CRT screening processes have drawbacks with regard to screen pattern distortion or excess time and material expenditure.
As per the above discussion, there exists a desiderata in the display industry for a reliable, high quality, pressure free, one pass application, with a minimum of material waste in the production of CRT phosphor screens.
It is therefore among the objects of the present invention to provide such a system for the production of CRT line screens without the use of multiple exposure photolithographic techniques or printing with apparatus which may distort under the pressures of printing. It is further among the objects of the present invention to provide for phosphor screen production with a minimum waste of the screen materials.